The present invention relates to a keyboard apparatus of, e.g., an electronic piano and an electronic organ.
Generally, in a keyboard apparatus of an electronic musical instrument, only a key switch is opened/closed by key operation. Therefore, a performer can produce a musical tone by applying a force to a key, which is a sum of a force required for pivoting the key and a force required for closing the key switch.
On the contrary, in an acoustic musical instrument such as a piano, a hammer (mass member which produces an inertial effect when a key is depressed) for striking strings must be driven upon depression of a key, thereby increasing a load applied upon depression of the key. Therefore, a performer feels key operation heavier than that of the keyboard apparatus of the above electronic musical instrument.
Recently, however, the electronic musical instrument can produce a musical tone similar to that produced by an acoustic piano. For this reason, demand has arisen for a keyboard apparatus providing the same key touch feeling as that obtained by a keyboard of the piano.
A conventional keyboard apparatus of an electronic musical instrument based on the above demand is disclosed in Japanese Patent Laid-Open (Kokai) No. 57-147691. In this apparatus, each key is pivotally disposed about a fulcrum, and a hammer which is formed independently of the key and is associated therewith is pivotally supported about a fulcrum. The hammer is provided to obtain a key touch feeling similar to that obtained by an acoustic piano and has the predetermined mass. The center of gravity of the hammer is located at an end corresponding to a rear end of the key, and a point of application of the hammer for pivoting the hammer in correspondence to pivoting motion of the key is arranged at an end opposite to that of the center of gravity and corresponding to a front end of the key.
Accordingly, when the key is depressed, the hammer is pivoted through the point of application, and when the key is released, the hammer and the key are pivoted clockwise by the weight of the hammer and returned to initial positions. That is, the depressed key is pivoted against the weight of the hammer, thereby obtaining the key touch feeling. In other words, the hammer produces the inertial effect upon depression of the key.
In this keyboard apparatus, however, the fulcrum of the hammer is located at the center of a longitudinal direction thereof. Therefore, upon depression of the key, the hammer is pivoted in a direction opposite to a direction along which the center of gravity thereof is lifted, i.e., a pivoting direction of the key, thereby lowering the position (moving distance) of the center of gravity. This is because the hammer abuts against the key which is moved downward when the center of gravity is lifted to a predetermined position.
As a result, if the weight of the hammer is maintained constant, in order to obtain a desired key touch feeling while assuring the sufficient displacement of the hammer, the height of the keyboard apparatus must be considerably increased. Therefore, an improvement is required to make the keyboard apparatus compact in size.